For example, a light source apparatus, employed as a light source of a liquid chromatograph, a semiconductor inspection device, or the like, comprises at least a gas discharge tube for emitting light having a prescribed wavelength, and a visible light source arranged at the rear side of the gas discharge tube and emitting visible light to the gas discharge tube. The gas discharge tube used for the light source apparatus comprises a cathode section and anode section for generating the discharge. A circular opening for passing through the visible light from the visible light source is formed in the anode section. The circular opening provided in the anode section is arranged at a position where the visible light passing through the circular opening can pass through a discharge narrowing hole (discharge path restricting section) for narrowing a discharge path between the anode section and the cathode section (For example, refer to Patent Documents 1 and 2).    Patent Document 1: Japanese Patent Application Laid-Open No. S59-215654    Patent Document 2: Japanese Patent Application Laid-Open No. H5-109389    Patent Document 3: Japanese Patent Application Laid-Open No. 2001-35238